From: Arjan van de Ven The quota code plays interesting games with the lock ordering; to quote Jan: | i_mutex of inode containing quota file is acquired after all other | quota locks. i_mutex of all other inodes is acquired before quota | locks. Quota code makes sure (by resetting inode operations and | setting special flag on inode) that noone tries to enter quota code | while holding i_mutex on a quota file... The good news is that all of this special case i_mutex grabbing happens in the (per filesystem) low level quota write function. For this special case we need a new I_MUTEX_* nesting level, since this just entirely outside any of the regular VFS locking rules for i_mutex. I trust Jan on his blue eyes that this is not ever going to deadlock; and based on that the patch below is what it takes to inform lockdep of these very interesting new locking rules. The new locking rule for the I_MUTEX_QUOTA nesting level is that this is the deepest possible level of nesting for i_mutex, and that this only should be used in quota write (and possibly read) function of filesystems. This makes the lock ordering of the I_MUTEX_* levels: I_MUTEX_PARENT -> I_MUTEX_CHILD -> I_MUTEX_NORMAL -> I_MUTEX_QUOTA Signed-off-by: Arjan van de Ven Acked-by: Ingo Molnar Cc: Jan Kara Signed-off-by: Andrew Morton --- fs/dquot.c | 2 +- fs/ext2/super.c | 2 +- fs/ext3/super.c | 2 +- fs/reiserfs/super.c | 2 +- fs/ufs/super.c | 2 +- include/linux/fs.h | 7 ++++++- 6 files changed, 11 insertions(+), 6 deletions(-) diff -puN fs/dquot.c~lockdep-annotate-the-quota-code fs/dquot.c --- devel/fs/dquot.c~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/fs/dquot.c 2006-06-06 16:16:02.000000000 -0700 @@ -1475,7 +1475,7 @@ static int vfs_quota_on_inode(struct ino goto out_file_init; } mutex_unlock(&dqopt->dqio_mutex); - mutex_unlock(&inode->i_mutex); + mutex_unlock_non_nested(&inode->i_mutex); set_enable_flags(dqopt, type); add_dquot_ref(sb, type); diff -puN fs/ext2/super.c~lockdep-annotate-the-quota-code fs/ext2/super.c --- devel/fs/ext2/super.c~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/fs/ext2/super.c 2006-06-06 16:16:02.000000000 -0700 @@ -1157,7 +1157,7 @@ static ssize_t ext2_quota_write(struct s struct buffer_head tmp_bh; struct buffer_head *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; diff -puN fs/ext3/super.c~lockdep-annotate-the-quota-code fs/ext3/super.c --- devel/fs/ext3/super.c~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/fs/ext3/super.c 2006-06-06 16:16:02.000000000 -0700 @@ -2614,7 +2614,7 @@ static ssize_t ext3_quota_write(struct s struct buffer_head *bh; handle_t *handle = journal_current_handle(); - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; diff -puN fs/reiserfs/super.c~lockdep-annotate-the-quota-code fs/reiserfs/super.c --- devel/fs/reiserfs/super.c~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/fs/reiserfs/super.c 2006-06-06 16:16:02.000000000 -0700 @@ -2204,7 +2204,7 @@ static ssize_t reiserfs_quota_write(stru size_t towrite = len; struct buffer_head tmp_bh, *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; diff -puN fs/ufs/super.c~lockdep-annotate-the-quota-code fs/ufs/super.c --- devel/fs/ufs/super.c~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/fs/ufs/super.c 2006-06-06 16:16:02.000000000 -0700 @@ -1269,7 +1269,7 @@ static ssize_t ufs_quota_write(struct su size_t towrite = len; struct buffer_head *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; diff -puN include/linux/fs.h~lockdep-annotate-the-quota-code include/linux/fs.h --- devel/include/linux/fs.h~lockdep-annotate-the-quota-code 2006-06-06 16:16:02.000000000 -0700 +++ devel-akpm/include/linux/fs.h 2006-06-06 16:16:02.000000000 -0700 @@ -563,12 +563,17 @@ struct inode { * 0: the object of the current VFS operation * 1: parent * 2: child/target + * 3: quota file + * + * The locking order between these types is + * parent -> child -> normal -> quota */ enum inode_i_mutex_lock_type { I_MUTEX_NORMAL, I_MUTEX_PARENT, - I_MUTEX_CHILD + I_MUTEX_CHILD, + I_MUTEX_QUOTA }; /* _